Chinese Journal of Polymer Science Vol. 26, No. 4, (2008), 443−454 Chinese Journal of Polymer Science ©2008 World Scientific NEW POLY(METHACRYLATE)S CONTAINING OXIME ESTERS MOIETIES BASED ON CYCLOHEXANON AND CYCLOPENTANON* Ibrahim Erol** Afyon Kocatepe Universty Faculty of Science and Arts, Department of Chemistry, Afyonkarahisar, Turkey Abstract The synthesis of two new methacrylates such as 2-[(cyclohexylideneamino)oxy]-2-oxoethyl methylacrylate (CHOEMA) and 2-[(cyclopentylideneamino)oxy]-2-oxoethyl methylacrylate (CPOEMA) are described. The monomers produced from the reaction of corresponding cyclohexanone O-(2-chloroacetyl) oxime and cyclopentanone O-(2- chloroacetyl) oxime with sodium methacrylate was polymerized in 1,4-dioxane solution at 65°C using AIBN as an initiator. The monomers and their polymers were characterized by IR, 1H- and 13C-NMR spectroscopy. The glass transition temperature of the polymers was investigated by DSC and the apparent thermal decomposition activation energies (Ed) were calculated by Ozawa and multiple heating rate kinetics (MHRK) method using the Shimadzu TGA thermobalance. By using gel permeation chromatography, weight-average (Mw) and number-average (Mn) molecular weights and polydispersity indices of the polymers were determined. The antibacterial and antifungal effects of the monomers and polymers were also investigated on various bacteria and fungi. The photochemical properties of the polymers were investigated by UV and FTIR spectra. Keywords: Methacrylate; Oxime esters; Activation energy; Thermal decomposition; Biological activitiy. INTRODUCTION Nowadays, the synthesis of functional monomers and their polymers and use in the synthesis of new functional polymers have attracted considerable interest. Methacrylic polymers find extensive applications in fiber optics, metal complexes, polymeric reagents, and polymeric supports[1−5]. Recent investigations report the use of oxime esters as irreversible acyl transfer agents where the leaving group, the oxime does not participate in the back reaction[6]. This methodology has been elegantly utilized for the preparation of chiral polymers[7], regioselective acylation of nucleosides and to obtain various nucleoside derivatives of medicinal significance[8]. In a previous report[9], methacrylate containing oxime ester moieties used as irreversible acyl transfer agents. Athawale and coworker reported the synthesis of geranyl methacrylate and (±) mentyl methacrylate by transesterification reaction using 2,3-butane dione mono-oxime methacrylate as acylating agents[10, 11]. O-acyloximes can be used as photobase generators and they have been proved to be quite efficient[12−17]. In case of phenyl acetyloximes, as a schematic process for amine production can be given. * This work was supported by Afyon Kocatepe Universty Research Fund (No. 06-FENED-09). ** Corresponding author: Ibrahim Erol, E-mail: [email protected]; [email protected] Received June 14, 2007; Revised July 12, 2007; Accepted July 13, 2007 444 Ibrahim Erol For carbonyl derivatives, direct hydrogen abstraction from the substrate to R leads to the formation of amine without requirement of water[18]. In previous studies, photolysis of oxime esters based on antraquinone were discussed as photo induced DNA cleaving agents for single and double strand scissions[19−21]. It is well known from the literature that the compounds containing oxime esters moiety have a strong ability to form metal complexes and exhibit a wide range of biological activities[21−25]. Thermogravimetric analysis (TGA) has been widely used to investigate the decomposition characteristics of many materials. Some methods have already been established to evaluate the kinetic parameters from thermogravimetric data[26–34]. In this paper, the TGA technique is applied to 2-[(cyclohexylideneamino)oxy]-2-oxoethyl methylacrylate (CHOEMA) and 2-[(cyclopentylideneamino)oxy]-2-oxoethyl methylacrylate (CPOEMA) homopolymers. The apparent activation energy was evaluated by isothermal thermogravimetric methods. The energies of activation at different steps were calculated by Ozawa and multiple heating rate kinetics (MHRK) methods[35]. The photochemical properties of polymers were investigated by ultraviolet spectrometer. EXPERIMENTAL Materials Cyclopentanonoxime, cyclohexanonoxime, chloroacetyl chloride, hydroxylamino hydrochloride and sodium hydroxide (Merck), sodium methacrylate, 1,4-dioxane, potassium carbonate, acetonitrile, anhydrous magnesium sulphate (Aldrich) were used as received. 2,2′-azobisisobutyronitrile was recrystallized from chloroform- methanol. Bactopeptone and glucose was obtained from Difco. All the other chemicals were analytical grade and used without any further purification. Characterization Techniques Infra-red spectra were measured on a Perkin Elmer Spectrum BX FT-IR spectrometer. 1H-NMR and 13C-NMR spectra were recorded in CDCl3 with tetramethylsilane as the internal standard using on Bruker GmbH DPX-400 500 MHz spectrometer. Thermal data were obtained by using a Shimadzu DSC-60 instrument and TGA-60 thermobalance in N2 atmosphere. Molecular weight; (Mw and Mn) of the polymers were determined by e waters 410 gel permeation chromatography equipped with a differential refractive index detector and calibrated with polystyrene standards. Electronic spectra were obtained on a Shimadzu UV 1700 spectrophotometer. Synthesis of cyclohexanone O-(2-chloroacetyl) oxime Synthesis of cyclohexanone O-(2-chloroacetyl) oxime was as follows: cyclohexanone oxime (1 mol) and K2CO3 (1 mol) was dissolved in 20 mL of anhydrous CH2Cl2 at 0°C, and then chloroacetyl chloride (1.1 mol) were added drop wise to the solution. The reaction mixture was stirred at room temperature for 12 h. (Scheme 1). The organic layer was washed several times with water and dried over MgSO4. Dichloromethane was evaporated. The organic layers were collected and the residue was distilled at 85°C at 666.7 Pa to give colorless liquid. Yield: 80%. The yield was 80%. Elemental analysis (%): C = 50.87 (found), 50.67 (calcd), H = 6.88 (found), 6.39 (calcd), N = 7.61 (found), 7.39 (calcd). IR (neat, cm−1): 1777 (C＝O oxime ester carbonyl), 1567 (C＝N―), 727 (C―Cl; no O―H absorption). Synthesis of cyclopentanone O-(2-chloroacetyl) oxime Synthesis of cyclopentanone O-(2-chloroacetyl) oxime was similarly synthesized expect that the product was distilled at 73°C at 5 mmHg. The yield was 80%. Elemental analysis (%): C = 46.90 (found), 47.88 (calcd), H = 5.63 (found), 5.74 (calcd), N = 7.94 (found), 7.98 (calcd). IR (neat cm−1): 1780 (C＝O for oxime ester carbonyl), 1570 (C＝N―), 735 (C―Cl; no O―H absorption). New Poly(methacrylate)s Containing Oxime Esters Moieties 445 Scheme 1 Synthesis of the CHOEMA monomer and its homopolymer Monomer synthesis The reactions paths for the synthesis of CHOEMA monomer are shown in Scheme 1. Cyclohexanone O-(2- chloroacetyl) oxime (1 mol), and sodium methacrylate (1.1 mol) were stirred in 50 mL acetonitrile at 75°C in a reflux condenser for 24 h in the presence of 100 × 10−6 hydroquinone as inhibitor. Then the solution was cooled to room temperature and neutralized with a 5% KOH solution. The organic layer was washed several times with water and the water layer was washed with diethylether a few times. The acetonitrile layer and diethyl ether layer were collected and dried over anhydrous MgSO4 overnight. Acetonitrile and diethyl ether were evaporated. The organic layers were collected and the residue was crystallized from ethanol. Elemental analysis (%): C = 60.49 (found), 60.24 (calcd), H = 7.18 (found), 7.16 (calcd), N = 5.54 (found) −l 5.85 (calcd). IR (KBr, cm ): 1780, 1728 (oxime ester and methacrylic carbonyl), 1633 (CH2＝C―), 1600 (C＝ 1 C), 1570 (C＝N). H-NMR (chemical shift, δ): 5.6 (CH2＝, 1H); 6.2 (CH2＝, 1H); 4.8 (―OCH2―, 2H); 2.1 13 (CH3―, 3H); 2.2−2.8 (CH2, 10H on the cyclohexane). C-NMR (chemical shift, δ): 169.0 and 173.0 (C＝O of esters); 131.0 (＝C); 122.1 (CH2＝); 22.1−37.8 ( cyclohexane carbons); 65.0 (―OCH2―); 21.5 (CH3). The CPOEMA monomer was similarly synthesized. Elemental analysis (%): C = 58.98 (found), 58.66 (calcd), H = 6.83 (found), 6.71 (calcd), N = 6.22 (found) −l 6.42 (calcld). IR (neat cm ): 1786, 1728 (oxime ester and methacrylic carbonyl), 1634 (CH2＝C―), 1600 (C＝ 1 C), 1573 (C＝N). H-NMR (chemical shift, δ): 5.6 (CH2＝, 1H); 6.3 (CH2＝, 1H); 4.8 (―OCH2―, 2H); 1.8 13 (CH3― 3H); 1.9−2.5 (CH2 on the cyclopentane ring). C-NMR (chemical shift, δ): 164.0 and 167 (C＝O of esters); 136.0 (＝C); 124.1 (CH2＝); 62.0 (―OCH2―); 24−391 (CH2 cyclopentane carbons ) 17 (CH3). Polymerization of the monomers Polymerization of CHOEMA and CPOEMA was carried out in glass ampoules under N2 atmosphere in 1,4- dioxane solution with AIBN (1% based on the total weight of monomers) as an initiator. The reacting components were degassed by threefold freeze-thawing cycles and then immersed in oil bath at 65°C for a given reaction time. The polymers were separated by precipitation in ethanol and reprecipitated from dichloromethane solution. The polymers were finally dried under vacuum to constant weight at room temperature and kept in a desiccators under vacuum until use. RESULTS AND DISCUSSION As shown in Scheme 1, the preparation of new methacrylate having pendant oxime ester moiety CHOEMA monomer was synthesized from cyclohexanone O-(2-chloroacetyl) oxime with sodium methacrylate, according to the usual method[36]. The CPOEMA monomer was synthesized and characterized by the same methods. The yields of the reactions in Scheme 1 are of medium quantity (80%). The structure of CHOEMA and 446 Ibrahim Erol CPOEMA were identified by elemental analysis, IR and NMR spectroscopy. Results were in good agreement with the structure of the compounds. The monomeric units of poly(CPOEMA) are presented in Scheme 2. Scheme 2 Structure of the poly(CPOEMA) Structural Characterization of the Monomers and Their Homopolymers The FT-IR spectra of the CPOEMA monomer and its polymer poly(CPOEMA) are shown in Fig. 1. In the IR spectrum of the polymer showed some characteristic absorption peaks at 1739 cm−1 (ester carbonyl stretching) 1781 cm−1 (oxime ester carbonyl stretching), 1565 cm−1 (C＝N).